The long-term objective of this project is to understand the role of monoamine oxidase A (MAO A) in mental disorders. MAO A is the key enzyme, which degrades serotonin (5-HT). This application focuses on the transcriptional regulation of MAO A. The new information obtained will provide new insights on the molecular basis of diseases associated with abnormal levels of 5-HT. It will also help develop a new series of MAO A inhibitors targeted at the transcriptional level. We have recently cloned a novel Repressor R1 specific for MAO A promoter. We have also found that steroids (androgen and glucocorticoid) activate the MAO A gene expression. With these new findings we hypothesize that the interactions among R1, Spl, a functional polymorphism, 30 bp variable number of tandem repeat (VNTR), steroid receptors and other associated proteins play important roles in the transcriptional regulation of MAO A. Specific aims are: 1. To investigate if Repressor R1 binds to Spl site or the GC rich region by site-directed mutagenesis, luciferase functional assay and gel shift assay. Human neuroblastoma (SK-N-BE (2)-C) and androgen dependent prostate carcinoma (LNCaP) cell lines will be used. The role of Cysteines on R1 function will be studied. The interaction between endogenous R1 and native MAO A promoter will be studied by chromatin immunoprecipitation (CHIP) assay. The biological function of R1 will be studied by RNA interference (RNAi) and serum starvation induced apoptosis. 2. To investigate the dynamic intracellular location of R1 protein in living cells by fusion R1 with enhanced Green Fluorescence Protein (eGFP). The brain regional distribution of R1 protein and mRNA will be studied by immunohistochemistry and in situ hybridization, respectively. They will be correlated with that of MAO A and B. The embryonic and postnatal development of R1 will be studied. 3. The effect of VNTR on R1 function and MAO A promoter activity will be investigated. Repressor R1 interacting proteins in SK-N-BE (2)-C cells will be co-immuno-precipitated using specific polyclonal R1 antibody developed in this laboratory.The proteins associated with R1 will be identified by their partial amino acid sequences by LC/MS/MS mass spectrometry. The validity and the function of these R1 interacting proteins will be investigated. 4. To identify the functional glucocorticoid (androgen) response element and to study the direct effect of AR/GR on MAO A promoter activity. The effect of VNTR on AR/GR activation of MAO A promoter will be studied. 5. To investigate if AR/GR indirectly activates MAC) A gene expression by interacting with Spl and other coactivators. The interactions among AR, GR, Spl and R1 on MAO A gene expression will be studied by luciferase assay (promoter activity), Northern blot (mRNA), Western blot (protein) and catalytic activity. AR (PC-3) and GR (Cos 7) negative cell lines will also be used. Co-regulators interacting with APJGR during agonist stimulated or basal state will be co-immuno-precipitated by AR or GR specific antibody. The validity and the function of identified protein(s) will be investigated.